In my U.S. Pat. No. 4,649,992 a device is described in combination with a catheter which is basically a compression spring retained between a partially inflated balloon and an abuttment immediately behind the balloon on the catheter shaft. The intent is to transport the spring prosthesis in this manner to the desired location and then after a successful angioplasty procedure release said spring prosthesis by totally evacuating said balloon, thus allowing said spring prosthesis to expand linearly and stay in place while the balloon catheter is withdrawn. This method is quite simple and its simplicity is very attractive; however, it has some drawbacks. One and foremost is the fact that the spring has a fixed diameter and as such is unable to fully conform to the inside wall of the vessel which at times is quite tortuous and thus could conceivably create a somewhat turbulant flow of blood, and possible thrombosis could in some cases result. Other patents, e.g. U.S. Pat. No. 4,553,545 teaches a different method where a relatively complex mechanical rotating device and co-axial cables are employed to achieve the necessary means to change the diameter of the implanted stent to a larger dimension at the point of implant. Still other patents, e.g. U.S. Pat. No. 3,868,956 describes a method wherein a temperature responsive metallic device is used and expanded after implant using external heat sources. All of the above mentioned devices present drawbacks of various magnitudes including blood coagulation and possible thrombosis and considerable complexity of procedure.
In angioplasty procedures at this time, in many cases restenosis occurs soon thereafter, which requires a secondary procedure or a surgical bypass operation. The implanted prosthesis as described herein will preclude such additional procedures and will maintain vascular patency indefinitely.
Depending on the size used, the stent according to this invention can also be efficacious in other similar applications, such as: repairs of aneurysms, support of artificial vessels or liners of vessels, initial repairs of dissections and mechanical suuport to prevent collapsing of dialated vessels. Still many other and similar applications will be satisfied by this invention without departing from the basic prewise and concept.
This stent and the method of its use particularly allows a single procedure to combine the essential angioplasty and a simultaneous implant of a permanent prosthesis designed and intended to prevent restenosis and further complications arising therefrom, also reducing the risk factor and trauma for the patient.
Another use of stents is for aortic dissection.
In the case of aortic dissection, especially a type III dissection of the descending aorta, there is no intravascular stent or prosthesis available, which is both long and flexible enough to repair a typical dissection extending the entire length from the point of origin down to the aortic bifurcation. Also, for the repair of the most difficult and most dangerous dissection, namely the type I which is that of the ascending aorta and the aortic arch, no stent is available today which could be used and be implanted intraluminarely for non-surgical repair of such a dissection. Most intravascular prosthesis and stent available today are of limited length and diameter and are especially limited in terms of flexibility and more specifically in terms of longitudinal flexibility unable to conform to tight bends and adhere to the walls of the intima and at the same time be flexible to stretch and move with each heartbeat such as experienced in the aortic arch.
Therefore, most such cases are treated medically. If surgery is necessary, it often requires the use of hypothermia and cardiopulonary bypass. Surgical procedures of this type involve high risk to the patient, a highly skilled team of cardiovascular surgeons and sophisticated equipment, because it requires the replacement of the affected region with an interpositional graft. High mortality and morbidity are associated with surgery in this region. This is especially true for the elderly and other poor candidates for a major surgery. The cost associated with such a surgical procedure is also very high.
Prior to the development of this invention, there has been no intravascular stent which would satisfy the following conditions necessary to contemplate a non-surgical repair of a dissecting aorta:
a) To be long enough to extend from the base of the aortic arch down to the aortic bifurcation. PA1 b) To be flexible longitudinally throughout its length. PA1 c) To be radially expandable easily, a small section at a time using common dilatation balloon or similar expanding device designed for that purpose. PA1 d) To be radially expandable to various diameters and to conform to tortuous conditions of a diseased aorta. PA1 e) To be non-obstructive to all branches. PA1 f) To be clearly visible on Floroscope both during deployment and post-operatively to visibly ascertain its condition, location and efficacy. PA1 g) To be implantable permanently, retrograde and be able to completely obliterate a false lumen of a dissection and to maintain patency of the main lumen as well, as the patency of all side branches throughout its length. PA1 1. Self-Expanding Metalic Stents for Small Vessels Radiology 1987- 162.469-472. PA1 2. Flexible Balloon-Expandable Stent for Small vessels, Radiology, January 1987. PA1 3. Intravascular Stents to Prevent Occlusion and Restenosis After Transluminar Angioplasty, N. E. J. of M., Mar. 19, 1987. PA1 4. U.S. Pat. No. 4,580,568, Percutaneous Endovascular Stent. PA1 5. U.S. Pat. No. 4,503,569, Transluminarely Placed Expandable Graft Prosthesis, Dotter 1985. PA1 6. U.S. Pat. No. 4,649,992, Catheter Arrangement Having a Variable Diameter Tip and Spring Prosthesis, Wiktor 1987. PA1 7. U.S. Pat. No. 4,681,110, Catheter Arrangement and Blood Vessel Liner, Wiktor 1987.
Other reference publications:
All of the above references describe and teach various methods of providing or otherwise offering and introducing stents of different types and designs for applications similar to the one described herein in this invention.